More progress.

- AMBUSH flag on nodes makes them blind and untargetable when getting `startnode` and `goalnode` for `FindPath()`. This is useful for indicating a node should be skipped when tele/portaling, so the current path can be preserved.
- Setup is simple: place nodes behind lines that tele/portal entities and mark them as AMBUSH.

Other changes:

- Restored global array since blockmap is not a viable option here.
- Added MAPINFO `pathing` flag which enables pathing by default.
- Added NOPATHING flag to disable pathing entirely, useful for maps that have pathing enabled.
- Added `ReachedNode(Actor mo)` virtual, responsible for handling node traversal.
- Nodes now make use of MeleeRange to limit their sight checking functions.

src/playsim/p_map.cpp

@@ -592,7 +592,7 @@ bool	P_TeleportMove(AActor* thing, const DVector3 &pos, bool telefrag, bool modi
 			thing->CheckSectorTransition(oldsec);
 		}
 	}
-
+	thing->CallReachedNode(thing->goal);
 	return true;
 }
 
@@ -2613,6 +2613,7 @@ bool P_TryMove(AActor *thing, const DVector2 &pos,
 				thing->LinkToWorld(&ctx);
 				P_FindFloorCeiling(thing);
 				thing->ClearInterpolation();
+				thing->CallReachedNode(thing->goal);
 				portalcrossed = true;
 				tm.portalstep = false;
 			}